quantitative anaylisis Flashcards
how can the concentration of a solution be measured
mols per dm3
how do you calculate moles of solute in a given volume of a known concentration
moles = conc x vol
when you have a smaller volume or large number of moles of solute what happens to the concentration
a smaller volume or larger number of moles of solute gives a higher concentration
when you have a large volume or small number of moles of a solute , what happens to the concentration ?
a larger volume or smaller number of moles of solute gives a lower concentration
to get from g/dm3 to mol/dm -3 what will you do
divide by molar mass in grams
to et frommol/dm -3 to g/dm3
multiply by molar mass in grams
to Carry out an accurate acid-alkali titration, using
burette, pipette and a suitable indicator what is the first step
add acid to the burret using a funnel and make sure to record the volume of the burette to start
to Carry out an accurate acid-alkali titration, using
burette, pipette and a suitable indicator what is the second step
add known volume of alkali to a conical flask and add some indicator
to Carry out an accurate acid-alkali titration, using
burette, pipette and a suitable indicator what is the third step
place conical flask on white tile (so you can see colour change clearly)
why do you place the concial flask on a white tile
so you can see the colour change more clearly
to Carry out an accurate acid-alkali titration, using
burette, pipette and a suitable indicator what is the fourth step
add acid to alkali until you reach the end point
to Carry out an accurate acid-alkali titration, using
burette, pipette and a suitable indicator, what is the fifth step
calculate how much acid has been added (titre)
to Carry out an accurate acid-alkali titration, using
burette, pipette, and a suitable indicator what is the sixth step
repeat until you get concordant results
why do we do titrations
to know the exact volume of an acid that reacts with the exact volume of alkali
if you only knew the concentration of the acid and wanted to calculate theconcentration of the alkali what would you do ?
- calculate moles of acid using
moles = concentration x volume
○ calculate the mole ratio of acid to alkali using the equation for the reaction - work out how many moles of alkali you have using the mole ratio and moles of acid
for example: if you have 5 moles of acid and the ratio of acid to alkali is 1:2, you will have 10 moles of alkali - calculate the concentration of the alkali using concentration = mol divided by volume
- follow the same method for if you have both concentrations but only one volume
what is the equation for percentage yirld
Percentage yield = amount of product produced / maxium amount of product possible x 100
how is the amount of product obtaind
Amount of product obtained is known as yield
what are causes of actual yield being less than theoretical yield
- incomplete reactions (not all of the reactants have reacted)
○- practical losses during the experiment (some product has been left in the weighing boat etc)
○ side reactions (some of the products react to form other products than those you wanted
what is atom economy
a measure of the amount of starting materials that end up as useful products
why is it important for reactions with high atom economy
Important for sustainable development and for economic reasons to use reactions with high atom economy
how do you calculate atom economy
atom economy
= (Mr of desired product from reaction/sum of Mr of all reactants) x 100
Explain why a particular reaction pathway is chosen to produce a specified product, given appropriate data such as atom economy,yield, rate, equilibrium position and usefulness of by-products
